1. Field of the Invention
The invention relates to a semiconductor component having a layer sequence for conversion of acoustic or thermal signals and electrical voltage changes to one another, as well as a process for its production.
2. Description of the Related Art
Such semiconductor components typically have a lower electrode, an upper electrode and a layer which is arranged between them and which is piezoelectrical in the situation where acoustic oscillations are produced or detected, and is pyroelectrical in the situation where thermal signals are produced or detected. In both situations, it is desirable for the crystal structure of the layer to have a pronounced texture in order to achieve a piezoelectrical or pyroelectrical coupling coefficient which is as high as possible. The higher this coupling coefficient, the more pronounced are the measurable electrical voltage changes in response to a predetermined acoustic or thermal signal.
A semiconductor component in which acoustic oscillations are produced by the piezoelectrical effect when an electrical voltage change is applied is described, for example, in Dubois, et al., “Properties of aluminum nitride thin films for piezoelectric transducers and microwave filter applications”, Appl. Phys. Lett. Vol. 74, No. 20, pages 3032-3034. A layer sequence which is used to produce acoustic oscillations comprises a lower and an upper electrode, and a piezoelectric layer composed of AlN which is arranged between them. In order to improve the texture, the lower electrode may be produced from platinum. Growth of the piezoelectrical layer on platinum results in the layer having a better texture, since platinum and AlN have similar crystal characteristics.